The Banbury® mixer is an industrial machine that fuses rubbers and heavy plastics together through pressure and heat. Invented in 1916 by Fernley H. Banbury, it revolutionized the automotive industry by making tire production simpler and less expensive. The mixer has been refined over the years but still uses the same basic mechanism of a hopper, pistons, and counter-rotating rotors. Heat and pressure are tightly controlled, and the mixer is used in many industries, including food and pharmaceuticals.
The Banbury® mixer is a type of industrial machine that can force rubbers and heavy plastics together, things that wouldn’t normally fuse together without a lot of pressure and energy. How it works is pretty simple. The mixer has a roughly cylindrical shape with a large hopper into which all the ingredients and additives are poured or placed; then, a series of pistons and rotators compress the materials as the pressure builds and the hopper begins to spin. In most cases, heat is also an important element, both through natural friction and through external input. The first models were designed for easy production and debuted in the early 1900s. Many sources also credit this mixer with helping the American auto industry explode a decade later, as it made mass production of tires much simpler and significantly less expensive. The basic Banbury® concept is still used in many places, although a number of modern tire mills and other rubber manufacturers have switched to new, usually digitally controlled alternatives.
Invention and basic concept
The mixer was invented by British entrepreneur Fernley H. Banbury in 1916 while living in the United States and working for an American manufacturing company who he thought could benefit from the machine’s efficiency and power. When his employer refused to patent the invention, Banbury left the company and filed for the patent himself. He later sold the design to Birmingham Iron Foundry, who manufactured the equipment under the Banbury® brand.
During the early years of the blender, many designs competed with the Banbury® blender, including single rotor blenders, but were commercially unsuccessful. In Europe and Asia, machines of similar design were produced in conflict with American patent rights.
Use in the automotive industry
The mixer has proven invaluable to many different industries, including those that focus on the manufacture of packaged foods and pharmaceuticals. However, it has had perhaps the largest and most profound impacts on the automotive industry. Goodyear was the first rubber manufacturer to take advantage of the superior mixing performance of the Banbury® mixer. The mixer was a game-changing event, as the automotive industry was growing rapidly, resulting in new demand for rubber tyres. Factories using this mixer were generally able to produce more in less time and with less energy, which created increased productivity and also helped reduce prices for consumers.
How does it work?
While the equipment has continued to be refined through many feature improvements over the years, the basic mechanism has remained unchanged. The Banbury® model has been specified through the development of many new synthetic materials, including high viscosity polymers.
The materials to be mixed are introduced through a hopper. A piston pushes the materials into the mixing chamber. Two counter-rotating rotors provide the mixing action, just like the double kneading hooks, and the mixed batch is discharged through an opening in the bottom of the mixing chamber to the next processing stage. Improvements over the years include many design changes to allow for easier operation and maintenance.
Heat and pressure controls
Heat transfer is tightly controlled in the modern Banbury® mixer. The rotors generate a lot of friction with the material, so mixing is generally an exothermic process, releasing heat to the environment. However, some blends absorb heat and become colder. In many machining operations, heat can be added to the system.
The internal pressure is also controllable and many mixing operations take place at high pressures and temperatures. This capacity is required for the mixer to act as a reactor chamber in the production of many polymers. Rubber compounding or rubber recycling is often referred to as “chewing and softening.” While these terms are perhaps most commonly used to describe the first steps of human digestion, rubber is usually not chemically modified; rather, it is simply made more malleable and flexible.
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